scholarly journals A quadratic model captures the human V1 response to variations in chromatic direction and contrast

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Michael A Barnett ◽  
Geoffrey K Aguirre ◽  
David Brainard
Keyword(s):  
Large Range ◽  
Visual Signals ◽  
Quadratic Model ◽  
Color Model ◽  
Important Goal ◽  
Vision Science ◽  
Free Parameters ◽  
Fmri Response ◽  
Chromatic Sensitivity ◽  
Good Agreement

An important goal for vision science is to develop quantitative models of the representation of visual signals at post-receptoral sites. To this end, we develop the quadratic color model (QCM) and examine its ability to account for the BOLD fMRI response in human V1 to spatially-uniform, temporal chromatic modulations that systematically vary in chromatic direction and contrast. We find that the QCM explains the same, cross-validated variance as a conventional general linear model, with far fewer free parameters. The QCM generalizes to allow prediction of V1 responses to a large range of modulations. We replicate the results for each subject and find good agreement across both replications and subjects. We find that within the LM cone contrast plane, V1 is most sensitive to L-M contrast modulations and least sensitive to L+M contrast modulations. Within V1, we observe little to no change in chromatic sensitivity as a function of eccentricity.

scholarly journals A Quadratic Model Captures the Human V1 Response to Variations in Chromatic Direction and Contrast

2020 ◽  
Author(s):  
Michael A. Barnett ◽  
Geoffrey K. Aguirre ◽  
David H. Brainard
Keyword(s):  
Large Range ◽  
Visual Signals ◽  
Quadratic Model ◽  
Color Model ◽  
Important Goal ◽  
Vision Science ◽  
Free Parameters ◽  
Fmri Response ◽  
Chromatic Sensitivity ◽  
Good Agreement

AbstractAn important goal for vision science is to develop quantitative models for the representation of visual signals at post-receptoral sites. To this end, we develop the quadratic color model (QCM) and examine its ability to account for the BOLD fMRI response in human V1 to spatially-uniform temporal chromatic modulations, systematically varying in their chromatic directions and contrasts. We find that the QCM explains the same, cross-validated variance as a conventional GLM, with far fewer free parameters. The QCM generalizes to allow prediction of V1 responses to a large range of modulations. We replicated the results for each subject and find good agreement across both replications and subjects. We find that within the LM cone contrast plane, V1 is most sensitive to L-M contrast modulations and least sensitive to L+M contrast modulations. Within V1, we observe little to no change in chromatic sensitivity as a function of eccentricity.

scholarly journals Adaptive Shell Spherical Reflector Actuated with PVDF-TrFE Thin Film Strain Actuators

Actuators ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 7
Author(s):  
Kainan Wang ◽  
Thomas Godfroid ◽  
Damien Robert ◽  
André Preumont
Keyword(s):  
Thin Film ◽  
Active Material ◽  
Quadratic Model ◽  
Influence Functions ◽  
Regularization Technique ◽  
Thin Polymer ◽  
Optical Modes ◽  
Electrostrictive Material ◽  
Ill Conditioning ◽  
Good Agreement

This paper discusses the design and manufacturing of a thin polymer spherical adaptive reflector of diameter D=200 mm, controlled by an array of 25 independent electrodes arranged in a keystone configuration actuating a thin film of PVDF-TrFE in d31-mode. The 5 μm layer of electrostrictive material is spray-coated. The results of the present study confirm that the active material can be modelled by a unidirectional quadratic model and that excellent properties can be achieved if the material is properly annealed. The experimental influence functions of the control electrodes are determined by a quasi-static harmonic technique; they are in good agreement with the numerical simulations and their better circular symmetry indicates a clear improvement in the manufacturing process, as compared to a previous study. The low order optical modes can be reconstructed by combining the 25 influence functions; a regularization technique is used to alleviate the ill-conditioning of the Jacobian and allow to approximate the optical modes with reasonable voltages.

Multilayer SIW Dual-Band Filters with Independent Band Characteristics and High Selectivity

Frequenz ◽  
2019 ◽  
Vol 73 (9-10) ◽  
pp. 293-300
Author(s):  
Dinghong Jia ◽  
Jianqin Deng ◽  
Yangping Zhao ◽  
Ke Wu
Keyword(s):  
High Selectivity ◽  
Bandpass Filter ◽  
Large Range ◽  
Metal Layer ◽  
Dual Band ◽  
Effective Dimension ◽  
Dual Mode ◽  
Transmission Zeros ◽  
Design Freedom ◽  
Good Agreement

Abstract This work presents an approach to developing dual-mode dual-band substrate integrated waveguide (SIW) bandpass filter based on multilayer process. TE102/TE201 and TE101/TE102 modes are used to feature the two passbands, respectively. To begin with, large range of band location ratios are decided by the effective dimension of the SIW resonator. With reference to the field distribution, independent coupling schemes of the dual-modes are then realized by slots or circular apertures etched on the middle metal layer. It allows to not only introduce a large design freedom of bandwidth but also keep compactness. Finally, source-load and mixed couplings are deployed to produce transmission zeros around the passband in providing a sharp selectivity in the two filters, respectively. The details to independently control the center frequencies and bandwidth of two passbands are also presented. A two-order double-layered and a triple-layered SIW dual-band bandpass filter are prototyped to evaluate the proposed design approach, respectively. Results show a good agreement between simulations and measurements. The proposed filter exhibits flexible design freedom, high selectivity as well as good out-of-band rejection.

scholarly journals Optimization of Bi2O3, TiO2, and Sb2O3Doped ZnO-Based Low-Voltage Varistor Ceramic to Maximize Nonlinear Electrical Properties

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Masoumeh Dorraj ◽  
Azmi Zakaria ◽  
Yadollah Abdollahi ◽  
Mansor Hashim ◽  
Seyedehmaryam Moosavi
Keyword(s):  
Low Voltage ◽  
Quadratic Model ◽  
Molar Ratio ◽  
Sintering Process ◽  
Spinel Type ◽  
Factors Affecting ◽  
Milling Method ◽  
Level 3 ◽  
Central Composite ◽  
Good Agreement

In ZnO-based low voltage varistor, the two essential features of microstructure determining its nonlinear response are the formation Bi-enriched active grain boundaries as well as a controlled ZnO grain size by secondary spinel-type phases. Besides, the microstructure and phase composition are strongly affected by the dopant concentration during sintering process. In this study, the optimal dopant levels of Bi2O3, TiO2, and Sb2O3to achieve maximized nonlinear electrical property (alpha) were quantified by the response surface methodology (RSM). RSM was also used to understand the significance and interaction of the factors affecting the response. Variables were determined as the molar ratio of Bi2O3, TiO2, and Sb2O3. The alpha was chosen as response in the study. The 5-level-3-factor central composite design, with 20 runs, was used to conduct the experiments by ball milling method. A quadratic model was established as a functional relationship between three independent variables and alpha. According to the results, the optimum values of Bi2O3, TiO2, and Sb2O3were obtained 0.52, 0.50, and 0.30, respectively. Under optimal conditions the predicted alpha (9.47) was calculated using optimal coded values from the model and the theoretical value is in good agreement with the value (9.43) obtained by confirmation experiment.

SELECTIVE REFLECTION FROM MERCURY AND CADMIUM VAPORS

1950 ◽  
Vol 28a (2) ◽  
pp. 93-112 ◽  
Author(s):  
H. L. Welsh ◽  
J. Kastner ◽  
A. C. Lauriston
Keyword(s):  
Resonance Frequency ◽  
Oscillator Strength ◽  
Large Range ◽  
Incident Light ◽  
Selective Reflection ◽  
Residual Intensity ◽  
Order Of Magnitude ◽  
Low Pressures ◽  
The Relationship ◽  
Good Agreement

Selective reflection from mercury and cadmium vapors in the neighborhood of the resonance lines was investigated quantitatively using incident light of continuous spectral distribution. For a given experimental arrangement the lowest vapor density (atoms per cubic centimeter) at which selective reflection could be detected at Hg 2537 Å, Cd 2288 Å, and Cd 3261 Å was inversely proportional to the oscillator strength (f-value) of the absorption line. Contours of the selective reflection of the Hg 2537 Å and Cd 2288 Å lines were obtained over a large range of vapor densities up to 80 × 1018 atoms per cc. At this density the cadmium reflection extended over several thousand cm.−1 compared to about a hundred cm.−1 for mercury. The general features of the reflection contours can be explained by the theory of reflection from an absorbing medium. Fitting a theoretical curve to the experimental reflection contour yields values of the oscillator strength and the damping constant. For Hg 2537 Å and Cd 2288 Å the f-values are 0.0268 and 1.40 respectively, in good agreement with those found by other methods. The damping constant, γ, varies as the square root of the number of atoms per cubic centimeter, indicating that the mechanism of selective reflection is not the same as that for absorption and emission. An empirical areal law for selective reflection confirms the relationship [Formula: see text]. A shift of the resonance frequency of the order of magnitude of the coupling shift calculated by Weisskopf was observed for Hg 2537 Å. Deviations from theory at both high and low pressures were observed for Cd 2288 Å. The low pressure deviation takes the form of a line of residual intensity at the resonance frequency, which may be due to a different kind of selective reflection.

scholarly journals A NEW ANSATZ FOR QUARK AND LEPTON MASS MATRICES

1992 ◽  
Vol 07 (26) ◽  
pp. 2429-2435 ◽  
Author(s):  
GIAN F. GIUDICE
Keyword(s):  
Vacuum Expectation ◽  
Cabibbo Angle ◽  
Expectation Values ◽  
Higgs Vacuum ◽  
Grand Unified Theories ◽  
Fermion Masses ◽  
Mass Matrices ◽  
Unified Theories ◽  
Free Parameters ◽  
Good Agreement

A new ansatz for quark and lepton mass matrices is proposed in the context of supersymmetric grand unified theories. The 13 parameters describing fermion masses and mixings are determined in terms of only 6 free parameters, allowing 7 testable predictions. The values of Vus, Vcb, Vub, mu, md, ms and mb are then predicted as a function of the 3 charged lepton masses, mc, mt and tan β, the ratio of Higgs vacuum expectation values. In particular the Cabibbo angle and ms/md are determined in terms of only lepton masses. All predictions are in very good agreement with experiments.

Kinetic modelling of the ignition delays in monomethylhydrazine/hydrogen/oxygen/argon gaseous mixtures

1998 ◽  
Vol 212 (6) ◽  
pp. 393-406 ◽  
Author(s):  
L Catoire ◽  
T Ludwig ◽  
G Dupré ◽  
C Paillard
Keyword(s):  
Pressure Range ◽  
Large Range ◽  
Kinetic Modelling ◽  
Reflected Shock Wave ◽  
Propulsion Systems ◽  
Gaseous Mixtures ◽  
Rocket Propulsion ◽  
Reflected Shock ◽  
Detailed Kinetic Model ◽  
Good Agreement

The objective of this study is to estimate the efficiency of ignition promotion or inhibition for H2=O2=Ar mixtures by monomethylhydrazine (CH3NHNH2, noted MMH), a propellant widely used in rocket propulsion systems. This is accomplished by computations performed with a detailed kinetic model. The model is validated with experimental ignition delays obtained behind a reflected shock wave in mixtures of MMH=O2=Ar, MMH=O2=H2=Ar and H2=O2=Ar. Good agreement (to about 25 per cent) is obtained between experimental and computed ignition delays with the mixtures of MMH=H2=O2=Ar at high temperatures (900–1170 K), in the pressure range 225–414 kPa. For the mixtures of H2=O2=Ar the agreement is also good over a very large range of temperatures (960±2300 K), pressures (up 5 MPa) and compositions (from highly diluted mixtures to undiluted). This model shows that, for the mixtures under consideration, MMH added in relatively small amounts (up to 10 per cent with respect to hydrogen) is an inhibitor or a promoter, depending on the amount added, under 1000 K and an inhibitor above 1000 K.

scholarly journals Optimization of sorting efficiency of size grading machine using oscillating sieve with swing along width direction

2019 ◽  
Vol 293 ◽  
pp. 04003
Author(s):  
Thatchapol Chungcharoen ◽  
Warunee Limmun ◽  
Watcharapong Chanpaka ◽  
Naruebodee Srisang
Keyword(s):  
Quadratic Model ◽  
Optimum Operating ◽  
Coffee Bean ◽  
Width Direction ◽  
Sorting Efficiency ◽  
Inclined Angle ◽  
Green Coffee Bean ◽  
Central Composite ◽  
Size Grading ◽  
Good Agreement

Grading according to the sizes is an important value adding technique for Robusta green coffee bean. Mechanical grading can increase the sorting efficiency and the need for workers is decreased. Therefore, the sorting efficiency of size grading machine was optimized based on inclined angle and oscillating speed. The Response Surface Methodology (RSM) combined with central composite design (CCD) was applied in the optimization of the sorting efficiency of the machine. A quadratic model was suggested for the sorting efficiency of size grading machine. The results showed that the optimum operating parameters for size grading machine using oscillating sieve with swing along width direction were inclined angle of 5.06 degree and oscillating speed of 183.28 rpm with a sorting efficiency of 79.99%. The high correlation coefficient (R2 = 0.9676) indicated that the data predicted using RSM were in good agreement with the experimental results.

Optimization of Cutting Parameters for Surface Roughness in Cold-Air Milling Ti6Al4V

2010 ◽  
Vol 431-432 ◽  
pp. 233-236
Author(s):  
Feng Jiang ◽  
Jian Feng Li ◽  
Jie Sun ◽  
Song Zhang ◽  
Lan Yan
Keyword(s):  
Surface Roughness ◽  
Material Removal ◽  
End Milling ◽  
Removal Rate ◽  
Cutting Parameters ◽  
Quadratic Model ◽  
Machining Center ◽  
Optimization Of Cutting Parameters ◽  
The Given ◽  
Good Agreement

In this study, orthogonal arrays were applied in the design of the experiments and Ti6Al4V end-milling experiments were performed on the DAEWOO machining center. The white light interferometer was used to obtain the average surface roughness (Ra). A quadratic model was proposed to fit the experimental data of the surface roughness. And the fit model was used to optimize the cutting parameters in the given material removal rate. Finally the verification experiments showed good agreement with the estimated results.

scholarly journals Radiation pressure measurement using a macroscopic oscillator in an ambient environment

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Mikko Partanen ◽  
Hyeonwoo Lee ◽  
Kyunghwan Oh
Keyword(s):  
Radiation Pressure ◽  
Pressure Measurement ◽  
Michelson Interferometer ◽  
Ambient Conditions ◽  
Experimental Accuracy ◽  
Light Pressure ◽  
Micromechanical Resonators ◽  
Free Parameters ◽  
Cryogenic Conditions ◽  
Good Agreement

AbstractIn contrast to current efforts to quantify the radiation pressure of light using nano-micromechanical resonators in cryogenic conditions, we proposed and experimentally demonstrated the radiation pressure measurement in ambient conditions by utilizing a macroscopic mechanical longitudinal oscillator with an effective mass of the order of 20 g. The light pressure on a mirror attached to the oscillator was recorded in a Michelson interferometer and results showed, within the experimental accuracy of 3.9%, a good agreement with the harmonic oscillator model without free parameters.

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